OCR Configuration for Advanced Reading

Input

The following vehicle registration record contains a mix of uppercase text, lowercase text, special symbols (@, $, #, |, ~, ^, *), and punctuation.

BlackListCharacters supplements the whitelist by actively excluding known noise symbols like `, ~, @, #, $, %, &, and *.

:path=/static-assets/ocr/content-code-examples/how-to/ocr-configurations-for-advanced-reading.cs

using IronOcr;

// Initialize the Tesseract OCR engine
IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    // Whitelist only characters that appear on license plates
    WhiteListCharacters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789- ",

    // Blacklist common noise characters
    BlackListCharacters = "`~@#$%&*",
};

var ocrInput = new OcrInput();
// Load the input image
ocrInput.LoadImage("advanced-input.png");
// Perform OCR on the input image with ReadPhoto method
var results = ocr.ReadPhoto(ocrInput);

// Print the filtered text result to the console
Console.WriteLine(results.Text);

Output

The whitelist filtering is clearly visible in the results:

• "Plate: ABC-1234" becomes "P ABC-1234". The lowercase word "late:" is dropped, while the plate number is preserved exactly.
• "VIN: 1HGBH41JXMN109186" becomes "VIN 1HGBH41JXMN109186". The colon is dropped, but the uppercase VIN and full number are kept.
• "Owner: john.doe@email.com" becomes "O". The entire lowercase email and punctuation are removed.
• "Region: CA-90210 | Zone #5" becomes "R CA-90210 Z 5". The pipe (|) and hash (#) are removed, while the uppercase letters and numbers survive.
• "Fee: $125.00 + tax*" becomes "F 12500". The dollar sign, decimal point, plus sign, and lowercase "tax" are all removed.
• "Ref: ~record_v2^final" becomes "R 2". The tilde (~), underscore, caret (^), and all lowercase characters are stripped.

The same WhiteListCharacters and BlackListCharacters approach works for any document type, not just license plates. The next section shows how to extend a read to detect barcodes and table structures in the same pass.

Input

single-line-label.png is a narrow shipping label with exactly one line of bold Courier text: SHIPPING LABEL: TRK-2024-XR9-001.

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    PageSegmentationMode = TesseractPageSegmentationMode.SingleLine,
};

using OcrInput input = new OcrInput();
input.LoadImage("single-line-label.png");

OcrResult result = ocr.Read(input);
Console.WriteLine(result.Text);

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    PageSegmentationMode = TesseractPageSegmentationMode.SingleLine,
};

using OcrInput input = new OcrInput();
input.LoadImage("single-line-label.png");

OcrResult result = ocr.Read(input);
Console.WriteLine(result.Text);

For a scanned page with irregular text placement, SparseText recovers more content than Auto.

Input

receipt-scan.png is a Corner Market thermal receipt with four line items (coffee, muffin, juice, granola bar), a dashed separator, subtotal, tax, and total. This is the kind of layout where fixed-block segmentation misses entries at different horizontal positions.

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    PageSegmentationMode = TesseractPageSegmentationMode.SparseText,
};

using OcrInput input = new OcrInput();
input.LoadImage("receipt-scan.png");

OcrResult result = ocr.Read(input);
Console.WriteLine(result.Text);

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    PageSegmentationMode = TesseractPageSegmentationMode.SparseText,
};

using OcrInput input = new OcrInput();
input.LoadImage("receipt-scan.png");

OcrResult result = ocr.Read(input);
Console.WriteLine(result.Text);

With layout segmentation tuned to the document type, the next step is controlling the output format for downstream processing.

Input

scanned-document.pdf is a single-page business letter from IronOCR Solutions Ltd. (dated 15 March 2024, reference DOC-2024-OCR-0315). The result is saved as searchable-output.pdf.

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    RenderSearchablePdf = true,
};

using OcrInput input = new OcrInput();
input.LoadPdf("scanned-document.pdf");

OcrResult result = ocr.Read(input);
result.SaveAsSearchablePdf("searchable-output.pdf");

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    RenderSearchablePdf = true,
};

using OcrInput input = new OcrInput();
input.LoadPdf("scanned-document.pdf");

OcrResult result = ocr.Read(input);
result.SaveAsSearchablePdf("searchable-output.pdf");

Output

The output is a PDF that looks identical to the input but contains a hidden text layer. Open searchable-output.pdf and use Ctrl+F to verify that the embedded text is searchable and copyable.

RenderHocr produces an hOCR document, an HTML file that encodes the text content together with bounding box coordinates for every word. This is useful when downstream tools need precise word positioning, for example, redaction engines or document layout analysis.

Input

document-page.png is a document page with the heading "Quarterly Summary Q1 2024" and two paragraphs of financial data covering revenue, operating costs, and growth drivers. The result is saved as output.html.

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    RenderHocr = true,
};

using OcrInput input = new OcrInput();
input.LoadImage("document-page.png");

OcrResult result = ocr.Read(input);
result.SaveAsHocrFile("output.html");

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    RenderHocr = true,
};

using OcrInput input = new OcrInput();
input.LoadImage("document-page.png");

OcrResult result = ocr.Read(input);
result.SaveAsHocrFile("output.html");

Output

output.html encodes each recognized word with its bounding box coordinates. Open the file in a browser to inspect the hOCR structure, or pass it to a downstream tool for layout analysis or redaction.

Both flags can be enabled at the same time if you need all three output formats (plain text, searchable PDF, and hOCR) from a single read call.

These output flags work independently of the language being read, including non-Latin scripts. The next section shows how to apply character filtering to Japanese text.

Input

The document contains a title (テスト), a Japanese sentence mixing Hiragana and Katakana with voiced-mark variants (プ, で), a price line with blacklisted noise symbols (★, ■) and Kanji (価格), and a memo line with another blacklisted symbol (§), more Kanji (購入), additional voiced-mark variants (プ, デ), and base Katakana (メモ, ール). The whitelist passes only base Hiragana, base Katakana, digits, and common Japanese punctuation; the three noise symbols are explicitly blacklisted.

The Unicode character ranges for Hiragana and Katakana are passed as string literals in WhiteListCharacters, with the noise symbols listed in BlackListCharacters.

:path=/static-assets/ocr/content-code-examples/how-to/ocr-configurations-for-advanced-reading-jp.cs

using IronOcr;
using System.IO;

IronTesseract ocr = new IronTesseract();

ocr.Configuration = new TesseractConfiguration
{
    // Whitelist only Hiragana, Katakana, numbers, and common Japanese punctuation
    WhiteListCharacters = "あいうえおかきくけこさしすせそたちつてとなにぬねのはひふへほまみむめもやゆよらりるれろわをん" +
                            "アイウエオカキクケコサシスセソタチツテトナニヌネノハヒフヘホマミムメモヤユヨラリルレロワヲン" +
                            "0123456789、。？！（）¥ー",

    // Blacklist common noise/symbols you want to ignore
    BlackListCharacters = "★■§",
};

var ocrInput = new OcrInput();

// Load Japanese input image
ocrInput.LoadImage("jp.png");

// Perform OCR on the input image with ReadPhoto method
var results = ocr.ReadPhoto(ocrInput);

// Write the text result directly to a file named "output.txt"
File.WriteAllText("output.txt", results.Text);

// You can add this line to confirm the file was saved:
Console.WriteLine("OCR results saved to output.txt");

Output

The full filtered output is available as a text file: jp-output.txt.

Because the whitelist includes only base Hiragana and Katakana characters, derived voiced-mark variants such as プ (pu) and デ (de) are dropped. Kanji characters like 価格 (price) and 購入 (purchase) are also excluded since they fall outside the whitelisted character set. Blacklisted symbols like ★, ■, and § are actively removed regardless of the whitelist.